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Membrane-dependent signal integration by the Ras activator Son of sevenless.

ABSTRACT: The kinetics of Ras activation by Son of sevenless (SOS) changes profoundly when Ras is tethered to membranes, instead of being in solution. SOS has two binding sites for Ras, one of which is an allosteric site that is distal to the active site. The activity of the SOS catalytic unit (SOS(cat)) is up to 500-fold higher when Ras is on membranes compared to rates in solution, because the allosteric Ras site anchors SOS(cat) to the membrane. This effect is blocked by the N-terminal segment of SOS, which occludes the allosteric site. We show that SOS responds to the membrane density of Ras molecules, to their state of GTP loading and to the membrane concentration of phosphatidylinositol-4,5-bisphosphate (PIP2), and that the integration of these signals potentiates the release of autoinhibition.

SUBMITTER: Gureasko J

PROVIDER: S-EPMC2440660 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature

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Membrane-dependent signal integration by the Ras activator Son of sevenless.

Gureasko Jodi J Galush William J WJ Boykevisch Sean S Sondermann Holger H Bar-Sagi Dafna D Groves Jay T JT Kuriyan John J

Nature structural & molecular biology 20080504 5

The kinetics of Ras activation by Son of sevenless (SOS) changes profoundly when Ras is tethered to membranes, instead of being in solution. SOS has two binding sites for Ras, one of which is an allosteric site that is distal to the active site. The activity of the SOS catalytic unit (SOS(cat)) is up to 500-fold higher when Ras is on membranes compared to rates in solution, because the allosteric Ras site anchors SOS(cat) to the membrane. This effect is blocked by the N-terminal segment of SOS, ...[more]

PMID: 18454158

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